Unit 6 Stoichiometry What Exactly Is Stoichiometry Composition
- Slides: 27
Unit 6 Stoichiometry
What Exactly Is Stoichiometry? Composition stoich – deals with mass relationships of elements in compounds (review Ch 3) Reaction stoich – deals with relationships between reactants and products
What You’ve Learned So Far… • Unit Conversions • Naming Chemical Compounds • Writing Chemical Formulas • The Mole • Writing Chemical Equations • Balancing Chemical Equations
Mole Ratios • Conversion factor relating amount of moles of any two substances
Example or or or
Molar Mass Ratios Al 2 O 3 – 101. 96 g/mol Al – 26. 98 g/mol O 2 – 32. 00 g/mol
Solving Stoichiometry Problems Must have: 1. Correct molecular formulas 2. Balanced chemical equation
Steps to Solving Problems 1. Write a balanced chemical equation 2. Identify information given in problem 3. Pick appropriate molar mass or mole ratio 4. Multiply numerators 5. Multiply denominators
Reaction Stoichiometry Mole-Mole-Mass or Mass-Mole Mass-Mass
Type 1 • Given quantity and unknown quantity in moles Quantity given (in mol) Quantity unknown (in mol)
Stoichiometry Examples: Type 1 (mol-mol) Example 1: The combustion of 2. 19 moles propane (C 3 H 8) produces how many moles carbon dioxide? Example 2: 41. 8 mol lithium hydroxide is combined with carbon dioxide to produce lithium carbonate and liquid water. How much water is produced from this reaction?
Type 2 • Given amount is in moles and unknown is mass in grams Amount given (in mol) amount unknown (in mol) mass unknown (in g)
Stoichiometry Examples: Type 2 (mol-mass) Example 3: In photosynthesis, plants use energy from the sun to produce glucose C 6 H 12 O 6, and oxygen from the reaction of carbon dioxide and water. What mass, in grams, of glucose is produced when 3. 00 mol of water react with carbon dioxide?
Type 3 • Given is amount in grams and unknown is amount in moles mass given (in g) amount given (in mol) amount unknown (in mol)
Stoichiometry Examples: Type 3 (mass-mol) Na. HCO 3 and Mg(OH)2 are both used as antacids – which is more effective per gram? Example 4: 1. 00 g Na. HCO 3 reacts with hydrochloric acid to produce sodium chloride, water, and carbon dioxide Example 5: 1. 00 g Mg(OH)2 reacts with hydrochloric acid to produce magnesium chloride and water
Stoichiometry Examples: Type 3 (mol-mass) Example 6 What mass of carbon dioxide, in grams, is needed to react with 3. 50 mol of water in the photosynthetic reaction?
Objective III. A. 3(i) – Use chemical equations to perform basic mole-mole, mass, and mass-mole computations for chemical reactions
Type 4 • Given is mass in grams and unknown is mass in grams mass given (in g) amount given (in mol) amount unknown (in mol) mass unknown (in g)
Stoichiometry Examples: Type 4 (mass-mass) Example 7 Tin (II) fluoride is used in some toothpastes. It is made by the reaction of tin with hydrogen fluoride according to the following equation. Sn(s) + 2 HF Sn. F 2(s) + H 2(g) How many grams of Sn. F 2 are produced from the reaction of 30. 00 g of HF with Sn?
Limiting Reagents III. A. 3(j) – identify limiting reagents and use this information when solving stoichiometry problems
What is a “limiting reagent”? • The reactant that is completely used up first in a chemical reaction
How to Find the Limiting Reagent 1. Analyze the question 2. Identify the given information 3. Write a balanced chemical reaction 4. Convert given information of Reactant 1 to Product A 5. Convert given information of Reactant 2 to Product A
Theoretical Yield III. A. 3(k) – compute theoretical yield, actual III. A. 3(l) – calculate (experimental) percent error and analyze yield, anderrors that experimental percent yield affect percent error
Theoretical Yield Using the limiting reagent to calculate the amount of product produced is called theoretical yield This is how much product could be made if the limiting reactant was totally consumed
Experimental Yield Also called the actual yield The amount of product actually collected in the laboratory is called the experimental yield
Percent Yield
Example – Limiting Reactant Aluminum reacts with chlorine gas to form aluminum chloride. In a certain experiment, 10. 0 g of aluminum is reacted with 35. 0 g of chlorine gas.
- What is composition stoichiometry
- How to find percent mass
- Stoichiometry deals with.
- Composition stoichiometry deals with
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